Quick A/C Question

[KenC]

There is absolutely no refrigerant in my system right now. Is it still imperative that I put a vacuum on the system before recharging it? That is, does there need to be negative pressure in the lines before charging it?

Also, which side do I charge? High or Low?

[DaN]

Well if you have a leak, it can be found by evacuting the system. If it holds vacuum for a while, it probably won't leak.
Also, if the system is under a vacuum, it will help to suck the charge in. I've charged a few e30s without a machine, and it takes forever to suck in a can.

You also want to get rid of moisture, so I would say a vacuum is a good idea.

If you are charging out of the can with it running, always use the LOW side.
If you have a machine, you want to charge on the high side to prevent liquid in the compressor. This is done with the engine off.

[KenC]

I don't have any leaks in the system.

So out of the can, I just turn the car and compressor on and then let it suck in? Sounds easy enough.

[KenC]

When you say 'forever', how long are you talking? It's taking me about 40 min per can...

[Roberte]

You almost always have to draw a vacuum on an AC system that has be opened to the atmosphere. That and change out your drier if its been opened for any length of time(probably no more than a few minutes depending how humid it is). Once a system is opened, the dessicant in the drier will suck up all of the moisture in the air and become waterlogged. At that point, it will do your car no good as it will cease to serve its purpose of drawing any moisture out of your freon. Even the smallest amount of water in your system will cause an ice crystal to form at your expansion valve and plug it. Once that happens (almost immediately if you have even the smallest amount of water in your system), you can put all the freon in the world in the system and it won't do you any good 'cause it won't go thru the valve. This is probably why its taking you 40 min per can. It shouldnt take more than a a few minutes (no more than 5 -15) to empty a can. Other than this, I don't have anything to add to what DaN said.